If you could travel faster than light is it true that you would go back in time?

Answer 1

If you could travel faster than light you would travel into the future.
Then you could stop, turn around, and record the past catching up to you!

Answer 2

Try to stick this out. It is going to be long, but I believe it will be worth it. It shows that traveling faster then light makes time a lot weirder than just going backwards.

Let’s go back to 1887 and the Michelson-Morley experiment. If you are unfamiliar with it, then here is a brief explination.

The Michelson-Morley experiment was intended to show Earth’s absolute motion through the ether. It did this by using a device that would split a light beam, shoot half off at 90◦ and then reflect it back. By measuring the time it took for the beam to travel they could determine if the device was moving because if the device was moving perpendicular to the beam, it would have a longer distance to travel (I could add a lot here, but trust me, this is basicly it. If you want more information do a search for Michelson-Morley experiment).

They took their measurements over a year while the Earth orbited the sun, and guess what. No difference was found! The experiment was a failure.

Why did it fail? Every one knew that the Earth moved and the experiment should have worked.

Everyone jumped on the bandwagon of coming up with different theories on why the experiment failed. Theories bounce back and forth like the beam of light, among them were:

1.)The experiment can be dismissed. Perhaps something was wrong with the equipment or the procedure or the reasoning behind it. Lord Kelvin and Oliver Lodge took that point of view.

However, this point of view is not tenable. Since 1887, numerous physicists have repeated the experiment, in 1960, masers were used for this purpose and an accuracy of one part in a trillion was achieved. But, always, the failure was repeated.

2.)Well, the experiment is valid and there is no ether wind for the following reasons.

a)The Earth is not moving. It is the center of the universe and everything revolves around it.

Let’s get real, ok. This would throw everything we ever learned about astronomy out the window.

b)The Earth does move, but in doing so it drags the neighboring ether with it so that it seems motionless compared with the ether at the earths surface.

British physicist George Stokes suggested this, but, this implies that there is friction between the Earth and the ether, and this would raise the question as to why the motions of heavenly bodies weren’t slowing down due to “ether drag”. Stokes’ notion died a quick and painless death.

c)The Irish physicist George FitzGerald suggested that all object (and therefore all measuring apparatus) grew shorter in the direction of motion in accordance to a formula which was easily derived.

The FitzGerald contraction (derived from the Michelson-Morley experiment) was one of the formulas that Albert Whatzname used in formulating his general theory of relativity.

d)The Austrian physicist Ernst Mach went right for the theart of the matter. He said there was no ether wind because there was no ether. What could be simpler?

This still doesn’t explain how light could cross a vacuum. (I could say more about Mach, but I have very little good to say about a man who believed that atoms were a convenient fiction.)

Lets go back an look at FitzGerald. What is easily derived for him is actually a bit complicated for most of us, and I am not going to show it all (I did once and bored three people to death and drove 4 to insanity), but the formula he came up with is:

L’ = L / sqr(1-v²/c²) (sqr means square root)

Now, as you can see as v increases then sqr(1-v²/c²) becomes less and less until if v = c then it becomes zero. That would mean that the length of an object traveling at the speed of light would have zero length!

Old Albert Whatizname showed that you could replace time with length and the formula would still hold and be true (no one has been able to disprove it yet), so that the faster you go, the slower time would pass (I am not going to go into the effect of gravitational fields and such, but it has been demonstrated experimently that the time dilation works).

Now, let’s look at what would happen if v > c. If you did that then (1-v²/c²) would be a negative number. If you try to take the square root of a negative number then you have an imaginary number!

So, what would happen to time at superluminal velocities. It does not become negative, it becomes imaginary (as do length and mass). What is imaginary time like?

Hey, don’t ask me. I showed it would not run backwards, that is all I was asked to do.

Answer 3

No. People always think that relativity suggests this sort of time travel is possible - it doesn't and it isn't.

However, if you shot off the earth in a rocket at speeds approaching those of light, time would slow down for you relative to an observer (us on earth). So in theory you could return to find that we've moved on 500 years in your absence, while you've only aged 20 years. Or something like that, can't remember the exact figures.

So, from that standpoint Special Relativity does suggest that time travel in to the future is possible, although not probable.

In to the past, however, no.

Answer 4

No its not true.

Because you cant accelerate up to the speed of light - period. Thats what Einstein said and all our current understanding confirms the point - there's no point in saying what would happen if you could do one impossible thing because then you're not even talking theoretical physics you're talking nonsense.

There are a category of theoretical particles that go faster than light called Tachyons though they're said to be able to go no slower than the speed of light - most physicists are very skeptical about their existence.

You cant go faster than light because if you could accelerate up to that speed - which you cant - your mass would be infinite so you'd need infinite energy to go faster - which does not exist and I cant see how anyone would accelerate when they had no concept of subjective time at all - the Universe would end (subjectively) in an instant if you could go at lightspeed.

People who say 'yeah you can' need to stop getting their Physics from Superman and Star Trek movies. If we ever do find ways to go back in time superluminal velocity will not be a way.

Answer 5

My understanding of this issue says no. For sure, travelling at light speed would alter time perception and the passage of time, but actually going back in time defies a very stead-sure logic. This logic is that what has happened in the past is a massive collection of physical changes and movements, and there is nothing that quantum dynamics can do to alter that and indeed return it to some previous setting. For that to occur you are talking about the realms of the supernatural.

Answer 6

NO. Of course not. Time is only what we call entropy - that means that everthing will wear out eventually, and the whole universe will slow down etc.Men only thought of time so they could get simulateousness meetings and would know, for instance when something would happen. When we eventually do go faster than light it will be shown that Einstein was wrong. You can quote me on that!

Answer 7

(1)"...If you could travel faster than light..." You can't!

(2)"...is it true that you would go back in time?..." See #1 above

Answer 8

big "if" that as its impossible for anything mith mass to travel faster than light... but if you were to travel at that speed took over a light beam and looked back you would be seeing the light from that time so your not effectivly in the past only looking into it...

Answer 9

well its true that looking at stars is like lokking a couple of seconds in the past because that isnt their current position because theyre so far away. so maybe since light has no mass it cant travel through time but maybe something with mass will.

Answer 10

Totally true! Go twice the speed of light for a week - look backwards with my super telescope and you will see yourself 2 weeks ago asking this question!